Direction controlling means for synchronous motors



3,146,867 DIRECTION CONTROLLING MEANS FOR SYNCHRONOUS MOTORS R. L. BERG Sept. 1, 1964 Filed Aug. 19, 1960 L .4 m 1|! M m a m m 2 Y B u l w m 4 3 2 2| INVEN TOR.

Berg

United States Patent 3,146,867 DIRECTION CONTRQLLING MEANS FOR SYNCHRONGUS MOTORS Ralph L. Berg, Crystal Lake, 111., assignor to Controls Company of America, Schiller Park, Ill., a corporation of Delaware Filed Aug. 19, 1960, Ser. No. 50,699 4 Claims. (Cl. 192-4) This invention relates to direction controlling means for use on self-starting electric synchronous motors of the type which, if not prevented from doing so, may start in either direction.

This invention is an improvement on Berg application Serial No. 806,029, filed April 13, 1959, now Patent No. 2,960,201, dated November 15, 1960. The direction controlling means employed in that device is satisfactory in operation but is somewhat troublesome in that it calls for critical production control. Thus, the rebound plate had to be accurately mounted on the gear train so that the friction between the plate and gear was sufiicient to assure that the plate followed the motion of the gear and was not excessive so that it would produce a drag on the gear train. Accurate setting of the plate proved costly in that there was no way of knowing that the plate would be properly mounted and all units had to be tested to be proven.

The primary object of the present invention is to provide an improved noiseless direction controller in which the drag between the gear and controller is predetermined.

The object has been realized by positioning a permanent magnet member on one gear (of ferrous material) of a gear train at a point in the train where it will engage and rebound from an adjacent gear if the train is started in the wrong direction. The member is so designed that it will impart a small magnetic load to the gear train eliminating gear train noise inherent in an unloaded train while assuring that the member follows the motion of the gear train when it rotates in the wrong direction.

As will be apparent hereinafter, this device is faster in operation due to the small amount of travel required before stopping rotation in the wrong direction.

A still further advantage is that the device is simply and readily mounted on the gear train with a predetermined load between the gear and member and affords a considerable cost reduction because of the elimination of any special procedure in setting the frictional load.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings, in which:

FIG. 1 is a top plan view of a synchronous motor gear train embodying the present invention.

FIG. 2 is a side elevation partly in section of a synchronous motor showing the present invention.

FIG. 3 is a perspective view of the control element.

Referring to the drawings, numeral 10 indicates generally a conventional, self-starting synchronous motor comprising stator 12 and a rotor shaft 14 carrying permanent magnet rotor 16 on which is fixed drive pinion 18. The stator and rotor are contained within housing 20 which includes a partition 22 provided with a central aperture 24 through which the drive pinion projects. This type of motor is reliably self-starting and, when ener gized, the rotor immediately rotates in synchronism with the current, but may start in either direction of rotation. Accordingly, the rotation direction controlling means of my invention is provided so that the rotor 16 will operate only in one direction to drive any suitable mechanism. When blocked from rotation in one direction the rotor will immediately start in the opposite or running direction.

The driving pinion 18 is operatively connected to a conventional speed reducing gear train indicated generally by 26 and operatively connected to driven shaft 27. The first gear 28 of the train is mounted on the plate 22 and drives through pinion 30 to a second gear 34 mounted on a shaft 35 which is provided with a direction control member 36. Gear 34 is made of steel or any other ferrous material and the direction controller either includes a permanent magnet portion or is made from a permanent magnet material as seen in FIG. 3.

The direction control member is positioned on the shaft 35 intermediate the second steel gear 34 and drive gear 49 so that it may slide on gear 34 and thus not interfere with the normal rotation of the gear train. As will be seen, control member 36 includes a thin flat base portion 42 provided with an aperture 44 which is adapted to receive shaft 35. The base is made from a permanent magnet material having a magnetic force sufiicient to respond to the movement of the steel gear. The magnet force of the control member serves a dual purpose: insuring that the control member will rotate with the gear when the gear rotates in the wrong direction and providing a small amount of continuous load in the running direction to eliminate gear train noise.

At one end of the base there is a projection 48 which may be a continuation of the base or attached to the base. This projection abuts the housing 20 in the running direction and limits the travel of the control member. The plate will not rebound upon impact with the housing because of the rigid nature of the projection. A vertical finger is provided adjacent the projection 48 and has a tip 51 that engages pinion 30 as shown by dotted line in FIG. 1, to prevent rotation in the wrong direction. Upon engagement, the finger engages the pinion gear causing the motor to reverse and rotate in the running direction.

In operation, the stator 20 is energized and the rotor 16 begins to turn. If it starts in the wrong direction, the first gear 30 will turn less than one-half revolution, whereupon tip 51 of the control member will engage the teeth of gear 30. In view of my prior patent, No. 2,766,863, dated October 16, 1956, abutments could be provided on the pinion though this is considered a more costly approach. When rotated in the running direction, the projection 48 hits the housing 20 and holds the plate 36 from further rotation. There will be no rebound of the plate when the projection hits the housing since the projection is a rigid structure and will not yield or flex to initiate any force in the opposite direction. The magnetic attraction between the permanent magnet control member and the steel gear is thereby continuously imparted to the gear train thus reducing inherent noise which is prevalent in an unloaded gear train. Since the magnetic attraction of a permanent magnet member can be easily controlled in production, it is a simple matter to achieve production uniformity.

Although but a single embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. In combination, a self-starting synchronous motor having a housing and a pinion on the rotor thereof, a first gear operatively engaging said pinion and driving a second gear, the second gear being mounted on a shaft and including a pinion gear, a permanent magnetic member comprising a body portion having a central aperture and a gear engaging means at one end, said body portion being mounted on the shaft intermediate the second gear and the pinion gear so that the engaging means will ena gage the first gear when rotated in one direction to block further rotation of the first gear and will contact the housing when rotated in the opposite direction to prevent further rotation of the member, said gear engaging means imparting a rebound to the gear train to start the gear train running in the opposite direction, said permanent magnetic member magnetically attracting the second gear and turning therewith when unrestricted, but slidably engaging the upper surface of the second gear when in contact with the housing, and the second gear to insure a small amount of resistance to motion of the gear train.

2. In combination with a self-starting synchronous motor having a housing and a pinion on the rotor thereof, a gear train operatively engaging said pinion, a direction controlling means comprising, a permanent magnet member mounted to slide on a gear in the gear train and magnetically attached thereto, means on the member for engaging an adjacent gear in the gear train in less than a half turn of rotation of the gear in the wrong direction, said engaging means also including means for preventing rotation of the member in the running direction while permitting continuous rotation in said direction of said gear.

3. The combination with a self-starting synchronous motor having a housing and a pinion on the rotor thereof, a gear train operatively engaging said pinion, of means for controlling the direction of rotation of said gear train comprising, a magnet member magnetically attached to a gear of said gear train and movable therewith, said magnet member including means movable by said gear into blocking engagement with another gear of said train for preventing continuous rotation of the gear train in the wrong direction if the gear train starts to rotate in the wrong direction, said preventing means rebounding under impact with said another gear to impart a rotational impulse to said first-mentioned gear in the running direction, and means to limit rotation of the magnet member with said gear in the running direction.

4. In a gear train having a ferrous gear driven by a synchronous motor, permanent magnet means magnetically attached to the ferrous gear and tending to rotate therewith, a portion of said magnet means being moved by said ferrous gear into blocking engagement with an adjacent gear of said train when said first-mentioned gear starts to rotate in the wrong direction whereby to prevent further rotation thereof in said wrong direction, a portion of the magnet means being adapted to engage an abutment when the ferrous gear carrying the same rotates in the running direction to stop rotation of said magnet means while permitting continuous rotation of the terrous gear in said running direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,147,204 Laird Feb. 14, 1939 2,722,297 Gates Nov. 1, 1955 2,960,201 Berg Nov. 15, 1960 

1. IN COMBINATION, A SELF-STARTING SYNCHRONOUS MOTOR HAVING A HOUSING AND A PINION ON THE ROTOR THEREOF, A FIRST GEAR OPERATIVELY ENGAGING SAID PINION AND DRIVING A SECOND GEAR, THE SECOND GEAR BEING MOUNTED ON A SHAFT AND INCLUDING A PINION GEAR, A PERMANENT MAGNETIC MEMBER COMPRISING A BODY PORTION HAVING A CENTRAL APERTURE AND A GEAR ENGAGING MEANS AT ONE END, SAID BODY PORTION BEING MOUNTED ON THE SHAFT INTERMEDIATE THE SECOND GEAR AND THE PINION GEAR SO THAT THE ENGAGING MEANS WILL ENGAGE THE FIRST GEAR WHEN ROTATED IN ONE DIRECTION TO BLOCK FURTHER ROTATION OF THE FIRST GEAR AND WILL CONTACT THE HOUSING WHEN ROTATED IN THE OPPOSITE DIRECTION TO PREVENT FURTHER ROTATION OF THE MEMBER, SAID GEAR ENGAGING MEANS IMPARTING A REBOUND TO THE GEAR TRAIN TO START THE GEAR TRAIN RUNNING IN THE OPPOSITE DIRECTION, SAID PERMANENT MAGNETIC MEMBER MAGNETICALLY ATTRACTING THE SECOND GEAR AND TURNING THEREWITH WHEN UNRESTRICTED, BUT SLIDABLY ENGAGING THE UPPER SURFACE OF THE SECOND GEAR WHEN IN CONTACT WITH THE HOUSING, AND THE SECOND GEAR TO INSURE A SMALL AMOUNT OF RESISTANCE TO MOTION OF THE GEAR TRAIN. 